A program of studies is proposed to investigated the role of polyamines (PA) and membrane bound transglutaminase (TGase) in the function of testicular receptors for gonadotropins (LH, FSH). PA and TGase effects will be determined on these specific aspects of receptor function which include LH and FSH binding, gonadotropin processing (degradation) and receptor turnover. Male rats will be utilized as the experimental model, although additional studies will be performed with immature calf testes. The initial phase of experimentation will utilize homogenates of testes parenchyma or leydig and Sertoli cells to study PA and TGase effects on LH and FSH receptor binding properties. These different cell types will be used to facilitate a comparison of the modulation of LH and FSH receptor function by PA and TGase. Specific parameters to be measured after experimental manipulation of membrane preparations will include gonadotropin association and dissociation constants, affinity constants and receptor number in membrane suspensions containing various levels of PA and TGase inhibitors. In addition, the Leydig and Sertoli cell TGase will be characterized with regard to substrate specificity and effects of inhibitors, polyamines and hormones on Km and Vmax. Experiments will be performed to determine if there are direct effects of FSH and LH on membrane TGase acivity. Studies with TGase inhibitors and polyamines will determine if effects on enzyme activity correlate with their effects on receptor function. The next phase of experimentation will utilize intact Leydig and Sertoli cell suspension cultures to study PA and TGase effects on gonadotropin degradation or internalization and gonadotropin receptor turnover. In addition, their effects on other post binding events such as increased in cAMP and adenylate cyclase activation will be determined. Finally, the extent of incorporation of labelled TGase substrates such as 14C-putrescine into Leydig and Sertoli cell membrane proteins will be measured and the proteins identified by two dimensional gel elctrophoresis. The long term goals of the investigator are to establish whichj specific biochemical processes are essential to gonadotropin receptor function and modulation of gonadotropin mediated cellular activation. Understanding these processes may provide new insight into the treatment of infertility as well as a better understanding of reproductive development leading to puberty and provide a greater variety of targets for contraception.